If Malaysia Airlines Boeing 777 is still missing more than 10 days after it disappeared from radar screens, it is because the transponder was turned off manually during the flight ! So why not make it impossible to disable these transponders ? A sensitive subject, and only after suffering many refusals from the industrial sector, Myriam Cormouls, Instructor at the National School of Civil Aviation agreed to explain why this is not possible today.
Myriam Cormouls Instructor : "Monitoring Sensors" - National School of Civil Aviation :
"There's the Annex 10 of the I.C.A.O. standards, a voluminous document, which stipulate the controls that must be provided on a transponder and therefore obligatory; meaning, a transponder must continually be operational or 'on alert'."
Myriam Cormouls Instructor : "Monitoring Sensors" - National School of Civil Aviation
"There have been some problems in the past with faulty transponders, and you can have transponders that will produce double flight paths, which give multiple responses to the monitoring sensor, for example, they will respond poorly to the sensor, and that will create two aircraft on the controller's screen rather than one for example ! You also have the altitude report that may be false, so you must be able to inhibit this, or turn the transponder off, however that doesn't happen often, in fact it's very rare!"
There are discussions circulating as to what could cause transponders permanently to be activated permanently and impossible to switched off.
Myriam Cormouls Instructor : "Monitoring Sensors" - National School of Civil Aviation
"In fact, no, because in normally, the transponder is switched on at the start up of the aircraft, after which, certain phases come into operation : both on the ground and in flight, but if if everything is functioning correctly, it's switched on all the time, therefore responding all the time, and up till now, there has never been saturation of the frequency band."
Myriam Cormouls Instructor : "monitoring sensors" - National School of Civil Aviation
"In exactly the same way as in your home, all equipment on board a 'plane is protected by circuit breakers, and therefore aircraft are necessarily protected by a 'breaker', a system that helps protect the supply cable in the case of short circuits, so theoretically the wiring should not overheat and certainly not to the point of creating a short-circuit."
Whatever the case, making it obligatory to have transponders which cannot be disabled in the cockpit is not for the foreseeable future. This would imply a change in the I.C.A.O. standards and involve a great deal of research and development on the part of the equipment manufacturers. One other solution : the installation in aircraft of a device capable of continual data transmission of flight data via satellite, but such a system would be inordinately expensive, estimated at $ 300 million, per year, per company.
